## ----raster-5, fig=TRUE , echo=TRUE, fig.width=6------------------------------
library(terra)
r <- rast(ncol=10, nrow=10, xmin=0, xmax=10, ymin=0, ymax=10)
values(r) <- 1:ncell(r)
ra <- aggregate(r, 2)
r1 <- crop(r, ext(0, 5, 0, 5))
r2 <- crop(r, ext(4, 10, 4, 10))
m <- merge(r1, r2, filename='test.tif', overwrite=TRUE)
plot(m)


## ----raster-6-----------------------------------------------------------------
r <- rast(ncol=3, nrow=2)
values(r) <- 1:ncell(r)
values(r)
s <- app(r, fun=function(x){ x[x < 4] <- NA; return(x)} )
as.matrix(s)
t <- lapp(c(r, s), fun=function(x, y){ x / (2 * sqrt(y)) + 5 } )
as.matrix(t)
u <- mask(r, t)
as.matrix(u)
v <- u==s
as.matrix(v)
w <- cover(t, r)
as.matrix(w)
x <- classify(w, c(0,2,1,  2,5,2, 4,10,3))
as.matrix(x)
y <- classify(x, cbind(id=c(2,3), v=c(40,50)))
as.matrix(y)


## ----raster-7-----------------------------------------------------------------
r <- rast(nrow=45, ncol=90)
values(r) <- round(runif(ncell(r))*3)
a <- cellSize(r)
zonal(a, r, "sum")


## ----raster-10----------------------------------------------------------------
r <- rast(ncol=36, nrow=18)
values(r) <- runif(ncell(r))
global(r, mean)
s <- r
values(s) <- round(runif(ncell(r)) * 5)
zonal(r, s, 'mean')
freq(s)
freq(s, value=3)
crosstab(c(r*3, s))